<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>边框</title>
    <style>
        div {
            color: red;
            font-size: 25px;
            text-decoration: none;
            text-align: center;
            line-height: 40px;
        }
    </style>
</head>
<body>
<div>aa</div>
</body>
</html>